Everest ES8311 audio CODEC

Required properties:

  - compatible: "everest,es8311"
  - reg: the I2C address of the device for I2C
  - spk-ctl-gpios: control spk enable/disable
Optional properties:

- clocks: The phandle of the master clock to the CODEC
- clock-names: Should be "mclk"
- adc-pga-gain: The PGA Gain of ADC, the value range is: 0(0dB) ~ 10(30dB),
                the step is 3dB.
- adc-volume: The volume of ADC, range is: 0x00(-95dB) ~ 0xff(+32dB), 0dB is 0xbf.
- dac-volume: The volume of DAC, range is: 0x00(-95dB) ~ 0xff(+32dB), 0dB is 0xbf.
- aec-mode: The string of description AEC path between ADC and DAC, It should be:
		"adc left, adc right",
		"adc left, null right",
		"null left, adc right",
		"null left, null right",
		"dac left, adc right",
		"adc left, dac right",
		"dac left, dac right"
	    And aec-mode is "adc left, adc right" by default, if the property
	    is not specified.
Example:

es8311: es8311@18 {
	compatible = "everest,es8311";
	reg = <0x18>;
	clocks = <&cru MCLK_I2S0_TX_OUT2IO>;
	clock-names = "mclk";
	adc-pga-gain = <0>;  /* 0dB */
	adc-volume = <0xbf>;  /* 0dB */
	dac-volume = <0xbf>;  /* 0dB */
	aec-mode = "dac left, adc right";
	spk-ctl-gpios = <&gpio2 5 GPIO_ACTIVE_HIGH>;
};